Dental Curing Light Having Unibody Design That Acts as a Heat Sink

ABSTRACT

A dental curing light includes a device body that efficiently conducts heat away from the light emitting diode portion of the curing light. The device body includes a proximal gripping end and a distal head end. The device body is formed from a thermally conductive body material. Excellent heat conduction away from the LED dies is achieved using a thermally conductive layer disposed over the device body. The thermally conductive layer serves as a conduit to quickly conduct heat away from the LED dies for dissipation within the material of the device body In this manner, the material of the device body serves as a highly efficient heat dissipater. The surface area coupling the thermally conductive layer to the device body is sufficiently large that a majority (e g, substantially all) of heat being conducted by the thermally conductive layer is transferred to the device body during operation of the device.

BACKGROUND

1. The Field of the Invention

The present invention generally relates to the field of light curingdevices. More particularly, the invention relates to light curingdevices including one or more light emitting diodes (e.g., LEDs) forproviding light curing wavelengths configured to cure polymerizablecompositions.

2. The Relevant Technology

In the field of dentistry, dental cavities or preparations are oftenfilled and/or sealed with photosensitive polymerizable compositions thatare cured by exposure to radiant energy, such as visible light. Thesecompositions, commonly referred to as light-curable compositions, areplaced within dental cavity preparations or onto dental surfaces wherethey are subsequently irradiated by light. The radiated light causesphotosensitive components within the compositions to initiatepolymerization of polymerizable components, thereby hardening thelight-curable composition within the dental cavity preparation or otherdental surface.

Light-curing devices are typically configured with an activating lightsource, such as a quartz-tungsten-halogen (QTH) bulb or light emittingdiodes (LEDs). QTH bulbs generate a broad spectrum of light that can beused to cure a broad range of polymerizable compositions. QTH bulbsgenerate substantial waste heat and require bulky surrounding structureto draw waste heat away from the bulb and to dissipate the waste heat.

Use of LED light sources has been a significant improvement in dentalcuring devices. LEDs are smaller than QTH bulbs and generally radiatelight at a narrow range surrounding a specific peak wavelength. Theyoften require significantly less input power to generate a desiredoutput of radiation. In addition, LED light sources provide a longerlife (e.g., tens of thousands of hours or more) than QTH bulbs. However,thermal management (e.g., dissipating heat) is still an issue withdevices which include LED light sources.

While prior LED curing light devices may produce less waste heat thanbulb curing devices, LED curing devices still tend to produce waste heatthat significantly raises the temperature of the LED and immediatelysurrounding structures during illumination. This increase in temperaturemay reduce the useful life of the LED. LEDs can burn out due tooverheating within a matter of minutes, requiring replacement of the LEDlight source if the heat is not dissipated.

SUMMARY

The present invention is directed to curing light devices thatefficiently dissipate heat away from a light emitting diode (LED) duringuse. The dental curing light devices include a device body having aproximal gripping end (i.e., handle portion) connected to a distal headportion by a neck portion. The device body is advantageously formed fromone or more thermally conductive body materials (e.g., thermallyconductive metal, polymer, ceramic, and/or thermally conductive ceramicfibers or nanomaterials). In one embodiment, the device body is onecontinuous piece with no joints (i.e., a “unibody” construction). All ora portion of the device body can be made from the thermally conductivebody material so long as the device body has sufficient thermalconductivity to dissipate the desired heat generated by the LED duringuse (i.e., with the device set to a maximum user selectable lightoutput). In one embodiment, an LED assembly is included on or within thedistal head portion of the device body. The LED assembly includes one ormore LED dies and a thermally conductive LED assembly substrate, and theone or more LED dies are electrically coupled to one or more contacts onthe LED assembly. The one or more LED dies are configured to emit aspectrum of light capable of curing a light curable composition. Theemitted spectrum may include one peak wavelength in an embodiment whereall LEDs are configured to emit at the same wavelength. Alternatively,the spectrum may include two or more different peak wavelengths where atleast one of the LED dies is configured to emit a different peakwavelength relative to at least one other LED die.

Heat dissipation from the LED assembly may be achieved using a thermallyconductive layer on the distal head portion of the device body betweenthe LED assembly and the thermally conductive body material of thedevice body. The thermally conductive layer is thin and therefore lackssufficient mass to serve as a heat sink; however, the thermallyconductive layer has a sufficiently high surface area and thermalconductivity to serve as a conduit to dissipate heat from the LEDassembly substrate into the body material of the device body. Thematerial of the device body serves as a highly efficient heatdissipater, thereby obviating the need for a separate internal heatsink. In one embodiment, advantageously, the dental curing device doesnot include an internal heat sink. The surface area coupling thethermally conductive layer to the device body is sufficiently large thata majority (e.g., substantially all) of the heat conducted away from theLED assembly by the thermally conductive layer is transferred to thedevice body.

In one embodiment, the thermally conductive layer may comprise aseparate piece that is secured to a portion of the device body and mayhave a thickness in a range from about 100 microns to about 1.5 mm andcan be made from one or more highly thermally conductive materials, suchas, but not limited to, beryllium oxide, diamond, aluminum nitride, orcombinations of these. In another embodiment, the thermally conductivelayer may comprise a very thin layer applied over at least a portion ofthe device body (e.g., by chemical or plasma vapor deposition or plasmaflame spraying). In such embodiments, the thickness may be only about0.05 micron to about 50 microns. The thickness and surface area of thethermally conductive layer is sufficient to ensure that most, if notessentially all, of the waste heat generated by the LED is transferredthrough the thermally conductive layer and dissipated into the bodymaterial. At moderate to low operating temperatures, the thermallyconductive layer can dissipate heat from the substrate of the LEDassembly at the same rate that heat is dissipated into the LED assemblysubstrate from the LED assembly, thereby allowing continuous moderate tolow temperature operation. The use of a thermally conductive layer incontact with sufficient surface area of the device body has been foundto provide surprisingly good heat dissipation from the one or more LEDs.The present inventive configurations essentially eliminate the longexisting problems associated with over heating in LED-based curinglights.

According to an alternative embodiment, individual LED semiconductordies may be directly mounted to the device body. In other words, thedevice body becomes the substrate on which the LED semiconductor diesare directly mounted. Power connections to the individual dies may bemade by electrically conductive metal traces (e.g., gold) disposed on orthrough the thermally conductive, electrically insulative layer formedover the device body. This is different from the above describedembodiment in which a relatively larger LED assembly including its ownLED assembly substrate is mounted on the distal head portion of thedevice body. In the alternative embodiment, the thin thermallyconductive, electrically insulative layer disposed over at least thedistal head portion of the device body is significantly thinner (e.g.,about 0.05 to about 50 microns) as compared to the thickness of an LEDassembly substrate (e.g., on the order of about 500-1000 microns). SuchLED substrates must be sufficiently thick so as to provide a degree ofprotection and strength to the overall LED package including one or moreLED dies mounted on the substrate. The thermally conductive/electricallyinsulative layer is sufficiently thick so as to electrically insulatethe dies from the underlying body, which may comprise metal. At the sametime, the layer is relatively thin (e.g., no more than about 50 microns,preferably no more than about 10 microns) so as to minimize resistanceto thermal conduction through this layer. Such an embodiment may exhibiteven further improved heat dissipation as the relatively thick substratelayer of the LED package assembly is eliminated.

In one embodiment, the curing light device includes an electronicsassembly that controls power to the one or more LED dies. Theelectronics assembly can be configured to drive the one or more LED diesat very high light intensities for extended periods of time withoutoverheating the LED die due to the ability to efficiently dissipate heataway from the LED. In one embodiment, the one or more LED dies canproduce a stable emission of light of at least about 2000 mW/cm², atleast 3000 mW/cm², or even greater than 3500 mW/cm². The LED curingdevices of the present invention can achieve stable light output withone or more LEDs that is as intense as, or even more intense than, lightgenerated by an arc lamp, which typically operates at 3500 mW/cm².Curing lights of the present invention dissipate heat through the body,allowing the device to be operated at high power and longer time periodscompared to conventional light curing devices.

In one embodiment of the invention, the electronics assembly isconfigured to minimize wavelength shifting of the output of the one ormore LED dies, even at high intensity light output. In this embodiment,the electronics assembly is configured to power the LED dies at amaximum power input that is substantially below the actual maximum orrated power input of the LED die. For example, the curing light caninclude an LED assembly that is rated at 10 watts, and the electronicsassembly can be configured to power the device at a maximum input powerof 2.5 watts. In one embodiment, the electronics assembly is configuredto power the one or more LED dies at a maximum power of less than about80% of the rated maximum input of the one or more LED dies, morepreferably less than about 50%, and most preferably less than about 40%of the rated maximum input of the one or more LED dies, while achievinga total light output of at least about 1000 mW/cm² from the light curingdevice, more preferably at least about 2000 mW/cm², even more preferablyat least about 3000 mW/cm², or even at least about 3500 mW/cm² of totallight output from the light curing device. In this way, the stability ofthe light output is maintained. For example, any wavelength shift isminimized so as to preferably be less than about 1%, more preferablyless than about 0.5%, and most preferably less than about 0.1%.

In one embodiment, the underpowered device can achieve a very highefficiency of total light output per watt of input power. In oneembodiment, the efficiency of the LED dies of the curing light can be atleast about 40%, at least about 60%, or even at least about 80%efficient. The highest efficiencies of the dental curing light devicemay be achieved with configurations including a reflective collarbetween the LED and the lens and/or include an anti-reflective coatingon the lens. Some embodiments may employ a light collimating photoniccrystal instead of a lens.

The device body has substantial heat dissipating capacity due to itsmuch larger size relative to the LED die(s) and/or LED assembly. Becausethe device body serves as a heat dissipater, no separate heat sink isrequired within the body of the device. Eliminating the heat sink (ascompared to typical prior art devices) can simplify the manufacturingprocess and allow for smaller, thinner, neck and distal headconfigurations that are more maneuverable within the patient's mouthwhile providing excellent heat dissipation. Providing a device body witha unibody construction helps maximize heat dissipation. It alsominimizes joints and seams where debris might collect.

In one embodiment, the head portion of the device body can have aremovable cup-like member that houses the LED assembly and at least aportion of the thermally conductive layer. The thermally conductivelayer is coupled to the LED assembly to facilitate heat transfer fromthe LED(s) of the assembly to the removable member and into the devicebody. The removable member can screw in or otherwise connect to a partof the distal head portion. When attached, the removable member becomesthermally integrated with the distal head portion, for example, byensuring high surface area contact between a corresponding part of thedistal head portion and the removable member such that efficient thermalconduction through the removable member and to the rest of the devicebody is maintained.

In one embodiment, the entirety of the device body including the handleportion, the neck portion, and the distal head portion, is formed of asingle piece of thermally conductive material. Exemplary metals that maybe used include, but are not limited to, aluminum, copper, magnesiumand/or alloys thereof. Exemplary thermally conductive ceramic materialsthat may be used include, but are not limited to, fibers ornanomaterials of carbon (e.g., graphene), boron, boron nitride, and/orcombinations thereof. Because the single piece body is only one piece,there are no seams or joints within the body itself, and otherinterfaces within the overall device are minimized. For example, thesingle piece body (i.e., unibody construction) may include an LED headassembly hole, a control assembly hole, and a power cord hole. The LEDhead assembly hole is configured to receive the removable memberincluding the LED assembly. In an embodiment in which individual LEDsemiconductor dies (absent any supporting LED assembly substrate) aredirectly mounted onto the head of the device body, the LED head assemblyhole may be omitted. Of course, in another embodiment individual LEDsemiconductor dies may be directly mounted onto the removable member,which is later coupled into the LED head assembly hole of the device.The control assembly hole formed within the handle portion of the bodyis configured to receive the electronics control assembly. The powercord hole formed at the proximal end of the body is configured toreceive a power cord that is coupled to the electronics controlassembly. Of course, the body may include other holes through the bodyto accommodate one or more screws or other attachment means to holdinternal components in place.

Because the entirety of the body is formed as a single piece in theunibody construction, heat dissipation throughout the body is improved,as seams within the body itself (i.e., where a first piece of the bodyabuts a second piece of the body) can create resistance to thermalconduction. The body advantageously has no such abutment seams. Theabsence of such seams within the body also provides for a robust dentalcuring light that can better withstand rough handling and/or dropping.

These and other benefits, advantages and features of the presentinvention will become more full apparent from the following descriptionand appended claims, or may be learned by the practice of the inventionas set forth hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS

In order that the manner in which the above recited and other benefits,advantages and features of the invention are obtained, a more particulardescription of the invention briefly described above will be rendered byreference to specific embodiments thereof which are illustrated in theappended drawings. Understanding that these drawings depict only typicalembodiments of the invention and are not therefore to be consideredlimiting of its scope, the invention will be described and explainedwith additional specificity and detail through the use of theaccompanying drawings in which:

FIG. 1 is a top perspective view of a dental curing light including adevice body having a proximal gripping end and a distal head end;

FIG. 2 is a bottom perspective view of the dental curing light of FIG.1;

FIG. 3 is a cross-sectional view of the dental curing light of FIG. 1;

FIG. 4 is a top perspective view of the device body of the dental curinglight of FIG. 1;

FIG. 5 is a bottom perspective view of the device body of the dentalcuring light of FIG. 1;

FIG. 5A is a cross-sectional view of the device body of FIG. 4;

FIG. 5B is a cross-sectional view of the distal head end portion of analternative dental curing light;

FIG. 5C is a cross-sectional view of the distal head portion of anotheralternative dental curing light having an alternative configuration;

FIG. 5D is a perspective view of the distal head end of the device bodyof FIG. 5B prior to attachment of the LED dies and associatedstructures;

FIG. 5E is a perspective view of the distal head end portion of FIG. 5Donce a thin electrically insulative thermally conductive layer has beenapplied;

FIG. 5F is a cross-sectional view of the distal head end portion of FIG.5E;

FIG. 5G is a perspective view of the distal head end portion of FIG. 5Eonce the LED dies have been directly mounted to the body;

FIG. 5H is a cross-sectional view of the distal head end portion of FIG.5G;

FIG. 5I is a cross-sectional view of the distal head end portion of FIG.5H once a reflective well has been built up around the LED dies;

FIG. 5J is a cross-sectional view of the distal head end portion of FIG.5I once a protective layer has been applied over the LED dies;

FIG. 6 is a cross-sectional view of a portion of the neck of the devicebody of FIG. 1 showing a scratch coating and a fluoropolymer coatingcovering the surface thereof;

FIG. 7 is a cross-sectional view of the neck and head portion of thecuring light of FIG. 1;

FIG. 8 is a perspective view of an LED assembly of the curing light ofFIG. 1;

FIG. 9 is a cross-sectional view of the LED assembly of FIG. 8;

FIG. 10 is a cross-sectional view of an alternative LED assemblyincluding a plurality of LED dies;

FIG. 11 is a partial exploded view of the neck and head portion of analternative embodiment showing a removable member housing an LEDassembly;

FIG. 12 illustrates the head and neck portion of FIG. 11 with theremovable member coupled into the well of the distal head portion; and

FIG. 13 illustrates a cross sectional view of the distal head portionand neck portion of the device of FIG. 12.

DETAILED DESCRIPTION I. Introduction

The present invention is directed to a dental curing light thatefficiently dissipates heat away from the light emitting diode (LED)portion of the curing light. The device body is formed from a thermallyconductive body material, (e.g., thermally conductive metal, polymer,ceramic, and/or thermally conductive ceramic fibers or nanomaterials).Excellent heat dissipation away from the one or more LEDs is achievedusing a thermally conductive layer coupled to the device body. Thethermally conductive layer is disposed over at least part of the distalhead portion of the device body so as to efficiently conduct heat awayfrom the one or more LEDs and into the device body. The thermalconductivity of the layer is sufficiently high that the thermallyconductive layer serves as a conduit to quickly conduct heat away fromthe substrate of the LED assembly or from direct mounted LED dies to thematerial of the device body, where the heat is dissipated. In thismanner, the body material of the device body can serve as a highlyefficient heat dissipater. The surface area of the thermally conductivelayer thermally coupling the LED assembly or direct mounted LED dies tothe device body is sufficiently large that a majority (e.g.,substantially all) of waste heat conducted into the thermally conductivelayer is quickly transferred to the device body for dissipation. Ingeneral, the surface area of the thermally conductive layer isadvantageously larger than the surface area of the substrate of the LEDassembly or direct mounted LED dies.

For purposes of this invention, the term “majority” means greater than50%.

For purposes of the invention, the term “highest power setting of thelight curing device” is the highest power setting that the device usercan select, not the theoretical maximum power that could be input intothe device's one or more LEDs.

Unless otherwise stated, “rated maximum power” shall refer to thegreater of the maximum power rating provided by the LED manufacturerhaving tested and rated the LED or the maximum power input as defined byan industry standard for testing and rating maximum power of LEDs.

II. Exemplary Dental Curing Lights

FIGS. 1-3 illustrate an exemplary dental curing light 100 including adevice body 102 having a distal head end 104 and a proximal gripping end106. Distal end 104 includes a neck portion 108 and a head portion 110.Distal end 104 is sized and configured to be inserted into the mouth ofa dental patient.

The dental curing light 100 also includes an electronics assembly 112positioned within a cavity of device body 102. The electronics assembly112 allows the dental practitioner to power on and off the dental curinglight 100 and control the intensity and duration of light output fromthe curing light 100. The electronics assembly can include hardware,circuitry and/or programming that allow the LED dies to be selectivelypowered and operated by a user. In one embodiment, the circuitry isprogrammable. Examples of programmable circuitry is described inApplicants co-pending U.S. Patent Application Ser. No. 61/174,562entitled, “Dental Curing Light Including Active And Activatable ProgramsFor Alternate Uses,” which is hereby incorporated by reference.

Curing light 100 includes a power cord 114 having a plug 116 that allowsthe device to be coupled to a power source. However, in an alternativeembodiment, the dental curing light can have a rechargeable battery thatpowers the electronics assembly. Device body 102 may include aprotective sleeve 118 attached to the proximal end. Protective sleeve118 may enclose the opening in the device body 102 through which cord114 passes and may also support cord 114 to prevent cord 114 fromdeveloping a short.

FIG. 2 shows a bottom perspective view of dental curing light 100. Headportion 110 includes an LED assembly 120. LED assembly 120 is configuredto emit light at one or more wavelengths suitable for curing a dentalcuring composition in the mouth of a dental patient. Holes 122 a and 122b allow the electronics assembly 112 to be secured to device body 102using, for example, a pair of screws.

FIG. 3 shows a cross-sectional view of dental curing light 100. Theelectronics assembly 112 includes a circuit board 124, power button 126,and intensity selector 128. Power button 126 allows the dentalpractitioner to power the curing light 100 on and off. Intensityselector 128 allows the dental practitioner to increase the intensity ofthe light being emitted from LED assembly 120 from a minimum poweroutput to a maximum power output. Actuating intensity selector 128increases the power delivered to LED assembly 120 through circuit board124. To decrease power intensity, the user can power the curing light100 off and back on again. Alternative control and operation modes willbe readily apparent to one of skill in the art. Wires 134 connectcircuit board 124 with LED assembly 120. Power cord 114 is alsoconnected to circuit board 124 to supply power to electronics assembly112.

In one embodiment, power cord 114 may comprise a high strength fiberand/or composite material. For example, power cord 114 may comprise amaterial including Kevlar and/or carbon fiber. Such materials provide ahighly flexible and supple power cord with exceptional strengthcharacteristics. In a preferred embodiment, the power cord 114 issecured to device body 102 using a knot 130. Knot 130 in power cord 114is positioned inside power cord hole 132 of device body 102. The knot130 abuts the device body around hole 132 and prevents the cord 114 frompulling through the hole 132. Knot 130 has been found to be highlyresistant to pulling through hole 132 and prevents breakage bydistributing a pulling force across a larger surface area. Knot 130 canoptionally be bonded or secured to device body 102 to prevent knot 130from being pushed further into the cavity of the device body.Surprisingly, the combination of a high strength cord material such asKevlar and/or carbon fiber and an internal knot have been found towithstand pull out forces of greater than about 50 pounds. Power cordsusing a knot may even be forcefully pulled upon (e.g., as might occur ifa practitioner tripped over the cord) without causing damage to theconnection between the power cord and the circuit board.

Circuit board 124 is electrically coupled to LED assembly 120. Theelectrical connection can be any connection suitable for use in a dentalapplication, including, but not limited to, electrically conductivetraces and/or wires. FIG. 3 illustrates wires 134 connecting circuitboard 124 to LED assembly 120.

A. Device Body

FIGS. 4, 5 and 5A illustrate the device body 102 of dental curing light100. Device body 102 includes a handle or gripping portion 106 that issized and configured for a dental practitioner to hold and manipulatewith the hand. Handle portion 106 is typically rounded and substantiallywider than neck portion 108, which is configured for insertion into amouth of a dental patient. Neck portion 108 is typically narrow andelongate for minimizing the space necessary to manipulate the curinglight 100 in the patient's mouth. Head portion 110 may be wider thanneck portion 108 to provide space for an LED assembly. Otherconfigurations (e.g., including direct LED die mounting and/or small,flexible organic LED dies) may have a head portion that is as narrow as,or even more narrow than the neck portion. In one embodiment, the devicebody may be elongate. While the devices described herein typicallyinclude structural features which configure the device for use in themouth of a patient, the device is not limited to use in the mouth. Head110 is illustrated with a recess or cavity 144 housing the LED assembly.However, in an alternative embodiment, the head 110 can have a flatsurface that supports the LED assembly (e.g., see FIGS. 5B-5C). Asdescribed more fully below, head 110 may also include a removable memberthat includes the LED assembly.

Device body 102 includes an internal cavity 136. Cavity 136 is sized andconfigured to house the electronics assembly used to operate the dentalcuring light 100, including powering LED assembly 120. Cavity 136 caninclude mounting points, grooves, and other features configured tosecurely receive an electronics assembly. In one embodiment, cavity 136includes a rim 138 that is configured to form a tight fit with acorresponding rim of electronics assembly 112 (FIG. 3) to ensure propersealing of cavity 136.

Handle portion 106 also includes an end opening 132 that provides apassageway from cavity 136 to an exterior of device body 102. Opening132 provides a passageway for power cord 114 as described above. Acollar 140 provides a connection for sleeve 118 that protects cord 114and seals opening 132, as described above with respect to FIG. 3.

Device body 102 may include a second passageway 142 that extends betweencavity 136 and the recess or cavity 144 in head portion 110. Passageway142 provides access between cavity 136 and 144 to deliver power to LEDassembly 120.

Device body 102 is constructed from a thermally conductive bodymaterial. Device body 102 may be formed of any suitable thermallyconductive body material, including, but not limited to, thermallyconductive metals, polymers, ceramics, fibers and/or nanomaterials(e.g., nanotube and/or nanosheet materials such as graphene). In oneembodiment, examples of suitable thermally conductive metals include,but are not limited to, aluminum, copper, magnesium and alloys thereof.In a preferred embodiment, the device body comprises an aluminum alloy.Aluminum alloys provide a device body that is sufficiently sturdy foruse in the dental practice where instruments are often subjected toconditions or situations that might damage, blemish or otherwise causedeformations. Aluminum alloys typically include alloying metals thatincrease the toughness and other properties of the material. Examples ofmetals that can be alloyed with aluminum or other base metals include,but are not limited to, zinc, magnesium, copper, titanium, zirconium,and combinations of these. In one embodiment, the aluminum alloy is analloy selected from the ANSI 6000 or 7000 aluminum alloy series. Adiscussion of ANSI 6000 and 7000 series aluminum and other suitabledevice body materials can be found in the “Handbook of Aluminum: Volume2: Alloy Production and Materials Manufacturing”, Jeorge E. Totten(editor), D. Scott MacKenzie, CRC; 1^(st) ed. (Apr. 25, 2003);“Introduction to Aluminum Alloys and Tempers”, J. Gilbert Kaufman, ASMInternational, 1^(st) ed. (Dec. 15, 2000); and “Aluminum and AluminumAlloys: ASM Specialty Handbook”, Joseph R. Davis; ASM International(Dec. 1, 1993), all of which are hereby incorporated herein byreference.

In one embodiment, the aluminum alloy may be ANSI aluminum alloy 6061,6033, 6013, 6020, 7075, 7068, and/or 7050 or any alloy having sufficientstrength and thermal conductivity characteristics. In yet anotherembodiment, the device body may comprise a thermally conductive ceramicfiber (e.g., carbon fiber, boron fiber, boron nitride fiber, or otherthermally conductive fiber). In yet another embodiment, the device bodymay comprise a thermally conductive nanomaterial (e.g., a graphenenano-sheet and/or nano-tube).

Examples of thermally conductive polymers include hydrophobic and/orhydrophilic polymers that have a thermally conductive filler materialincluded therein, such as, but not limited to, nanomaterials of carbon,beryllium oxide, boron nitride, and/or other thermally conductiveceramics and/or thermally conductive particulate metals. Examples ofthermally conductive ceramics include aluminum nitride, beryllium oxide,silicon carbide, and boron nitride.

The device body can include any of the foregoing thermally conductivebody materials alone or in combination. Although perhaps less preferred,the device body may include non-thermally conductive materials so longas substantial portions of the device body are thermally conductive soas to dissipate the desired amount of heat from the one or more LEDswhen powered.

The device body can be a solid material in portions thereof and/orhollow in other portions. For example, the head and neck portions may besolid particularly in embodiments where the LED assembly is notremovable and/or where the LED dies are directly mounted onto thethermally conductive layer. Hollow portions of the device body canprovide locations for housing various components, such as, but notlimited to, electrical components.

In one embodiment, the device body has a unibody construction. At leasta portion of the handle 106, neck 108, and head 110 can be formed from asingle piece of body material. In a preferred embodiment, substantiallyall of the handle portion, neck portion and head portion comprise asingle piece of body material. The device body 102 serves as a heatdissipater for the one or more LEDs. Forming the body from a singlepiece of thermally conductive material maximizes heat conduction intothe device body 102, where it can quickly be dissipated throughout thebody and into the air.

Such a unitary body is shown in FIGS. 4, 5, and 5A. The entirety ofdevice body 102, including handle portion 106, neck portion 108, andhead portion 110, is formed of a single piece of thermally conductivematerial (e.g., preferably a metal such as an aluminum alloy). Becausesingle piece body 102 is only one piece, there are no seams within thebody 102 itself, and other interfaces are minimized. For example, theillustrated example includes an LED head assembly hole 144, a controlassembly hole 136, and a power cord hole 132. The LED head assembly hole144 is configured to receive an LED head assembly 120 (FIG. 3). Thecontrol assembly hole 136 formed within the handle portion 106 isconfigured to receive an electronics control assembly 112. Power cordhole 132 formed at the proximal end of body 102 is configured to receivea power cord 114 that is coupled to electronics control assembly 112(FIG. 3).

The unibody construction shown in FIGS. 4, 5 and 5A eliminates seams andjoints through the body 102 itself, and minimizes the presence ofinterfaces within the device 100 overall. Because the entirety of thebody 102 is formed as a single piece, heat dissipation throughout thebody 102 is improved, as seams or joints within a device body (i.e.,where a first piece of the body abuts a second piece of the body) cancreate resistance to thermal conduction. The absence of such seamswithin the body 102 also provides for a robust dental curing light thatcan withstand rough handling and/or dropping. It also reduces joints orcrevices where debris or bacteria might collect.

Although LED head assembly 120 comprises a separate piece in theillustrated embodiment (e.g., so as to provide advantages of quickreplacement if an LED or other LED assembly component fails), there isonly a single additional seam over which heat must be conducted, as heatis conducted from the LED head assembly 120 into unitary body 102. Thepresence of the single seam is a significant improvement overconfigurations in which the body comprises multiple pieces abutted andjoined together. Such an embodiment easily allows removal andreplacement of the LED head assembly (e.g., in the case of a failed LEDor in order to upgrade the LED head assembly with a different one). Inan alternative embodiment, even the LED head assembly may be integratedinto the single piece body such that there is no seam over which heatmust be conducted from the one or more LED dies into the remainder ofthe unitary body. Such a configuration is shown and described inconjunction with FIG. 5B.

Typically, the LED head assembly 120 comprises the same material as thebody 102. In preferred embodiments, these structures are formed of metal(e.g., an aluminum alloy), and act as the only heat sink into whichwaste heat generated by the one or more LED dies is dissipated.Preferably, the LED head assembly 120 is relatively small in mass ascompared to the mass of body 102 in embodiments in which they areseparate pieces. For example, the LED head assembly 120 has a mass nomore than about 25% of the mass of body 102, more preferably no morethan about 10% of the mass of body 102, and most preferably no more thanabout 5% of the mass of body 102. As such, the mass and heat dissipatingcharacteristics of the LED head assembly 120 are minor or insignificantas compared to body 102. LED head assembly 120 has a relatively smallmass and simply acts to quickly facilitate conduction of heat acrossassembly 120 to body 102, where it can be dissipated. As a practicalmatter, body 102 acts as the only heat sink.

Device body 102 preferably comprises a metal such as aluminum, copper,magnesium, or alloys including such metals. Particularly preferredaluminum alloys include ANSI aluminum alloys 6061, 6033, 6013, 6020,7075, 7068, and/or 7050. 7075 is an exemplary aluminum alloy that may beused in the manufacture of body 102. A single piece of aluminum alloymaterial may be machined, cast or molded, resulting in a unitary singlepiece body (i.e., unibody construction). Machining is preferred, as itprovides a body with very narrow tolerance dimensions. Machined alloysoften also exhibit greater density and strength as compared to metals oralloys formed by alternative methods (e.g., casting or metal injectionmolding).

FIG. 5B illustrates an alternative embodiment 100′ that does not includea separate LED head assembly, but in which LED dies 160′ are directlymounted onto the distal head end 110′ of the one piece body itself. As aresult, the single piece thermally conductive body 102′ does not includean LED assembly hole configured to receive an LED assembly, as the LEDdie(s) are directly mounted onto the body 102′. The head and neckportions of the device 100′ may be solid, while the proximal handleportion may include a cavity for housing electronic control components.Although such a configuration does not as easily allow replacement ofone or more dead LED dies or the easy replacement/upgrade of an LEDassembly, it does offer the advantage of no seam over which heat must beconducted away from the LED dies into the single piece body. Inaddition, there are advantageously no intermediate substrate layers inbetween the LED die 160′ and the underlying mounting layer 154′. Theelimination of such layers (e.g., primary heat sinks and/or relativelythick substrates) further increases the heat dissipation ability of thedevice as there are fewer interfaces through which heat must beconducted. The reduction in the presence of such interfaces may furtherreduce the need for relatively inefficient thermal greases and/orepoxies typically used at the interface between such layers.

Such a configuration is also extremely robust and resistant to damage,as it eliminates relatively bulky LED assembly 120, which includes thickassembly substrate 162 and package 164 (FIG. 8). Advantageously, thereare no substrate layers between the semiconductor die 160′ and the thinthermally conductive/electrically insulative layer 154′ over thethermally conductive body. Because each LED die 160′ is directly mountedto the thermally conductive/electrically insulative layer 154′ of thethermally conductive body 102′, resistance to thermal conduction ofwaste heat generated from each die to the thermally conductive body 102′is advantageously minimized.

As seen in FIG. 5B, at least the distal head end 110′ of unitary body102′ includes a thin, electrically insulative and thermally conductivelayer 154′ (e.g., an oxide or nitride of the underlying metal bodysubstrate) formed directly over the unitary body 102′. The LED dies 160′(without any assembly substrate) are mounted on layer 154′ so as toelectrically isolate them from the underlying (e.g., metal) substrate.This thin layer 154′ has a thickness between about 0.05 micron and about50 microns, which is sufficient to electrically isolate the LED dies160′ from the underlying unitary body substrate 102′. In someembodiments, it is advantageous for layer 154′ to be no thicker thanrequired for electrical insulation because the thermal conductivity ofthis layer may be significantly less than that of the underlying metalbody 102′. For example, the thermal conductivity of aluminum alloy 7075(e.g., the body 102′) is about 130 W/m-K, while that of aluminum oxide(e.g., layer 154′) is only about 40 W/m-K. Such issues may be lessimportant depending on the material of layer 154′. For example, aluminumnitride has a thermal conductivity of about 285 W/m-K. The thickness oflayer 154′ is greatly exaggerated in the Figure for clarity purposes.

Although electrically insulative/thermally conductive layer 154′ mayhave a thickness as low as about 0.05 micron or as thick as about 50microns, more preferably the thickness of layer 154′ is between about0.1 micron and about 10 microns, and most preferably between about 0.2micron and about 1 micron.

Layer 154′ is also beneficial in minimizing effects of the differencesin thermal expansion of the underlying metal or other conductivematerial body relative to that of the LED dies 160′. In other words,there is often a significant difference between the relatively lowcoefficient of thermal expansion of the LED die relative to the highcoefficient of thermal expansion of a metal body material. The materialof layer 154′ may be selected so as to exhibit a coefficient of thermalexpansion that is between that of the body material (e.g., a metal) andthat of the one or more LED dies, helping to minimize any tendency ofthe underlying body to form micro-cracks and fissures after prolongedtemperature cycling during use. In some embodiments, the thermallyconductive layer (e.g., 154′ or 154) may even be omitted. For example,where the body (e.g., 102′) is formed of an electrically insulativematerial (e.g., carbon fiber, boron nitride, and/or graphene) thethermally conductive layer may be omitted as a result of the excellentthermal conductivity provided by the underlying body material (e.g.,body 102′), and the LED dies (e.g., 160′) may be directly mounted ontothe electrically insulative, thermally conductive body material (e.g.,body 102′). Mounting may be accomplished chemically (e.g., by use of athermally conductive epoxy) and/or by mechanical compression (e.g.,using a thermally conductive grease and/or gel).

According to one embodiment, layer 154′ may be applied over the entireunitary metal body substrate 102′ or a substantial portion thereof.Layer 154′ may be applied by chemical or plasma vapor deposition, plasmaflame spraying, or other techniques that will be apparent to thoseskilled in the art. Power connections to the LED semiconductor dies 160′may be made through gold or other conductive metal traces 170′ laid down(e.g., by a deposition process) over the layer 154′, electricallyinsulating the traces 170′ from the underlying body 102′. In order toprotect traces 170′ from damage, the traces may be sandwiched betweenlayer 154′. For example, the layer 154′ may actually be laid down as twolayers with a total thickness as described above, with the conductivemetal traces 170′ sandwiched in between. Such a configuration is shownin FIG. 5B. As illustrated, traces 170′ may include one or more powerconnection points 171′ where trace 170′ is exposed so as to electricallycontact LED dies 160′. In the illustrated embodiment, the neck anddistal head end may be solid rather than hollow (a hollow example isshown in FIG. 7), as power connections are made by traces 170′ ratherthan wires fed through a hollow head. Providing a solid neck and headmay further increase heat dissipation ability of the unitary body, as asignificant fraction of the body's mass is available directly adjacentto the heat generating LED dies 160′. Only a single power connectionpoint 171′ is shown for each LED semiconductor die 160′ for purposes ofclarity, although another connection point (or even more than two) maybe provided in a different or even the same cross-sectional plane.

Any of the described embodiments may further include a photonic crystalfor collimating light. Referring to FIG. 5B, dental curing light 100′ isillustrated as further including a photonic crystal 150′, which acts asa light collimator. Photonic crystals are periodic opticalnano-structures that affect the motion of photons in a similar way assemiconductor crystals affect the motion of electrons. By way ofexample, some naturally occurring materials, such as opal, peacockfeathers, butterfly wings, and iridescent beetles include photonicmaterials. A photonic crystal operates on a quantum level to captureincoming photons and refract them in a particular way. Photonic crystalsare customized to specific wavelengths or ranges that they capture andcollimate. Because of this, the crystal would be selected to capture andcollimate light of the desired wavelengths (e.g., anywhere between about350 nm and about 490 nm—the crystal is matched to the LED die).

As compared to a traditional lens, photonic crystals are more efficientat collimating light. In addition, it requires less space so as toprovide better focusing/collimating ability in the small availablespace. Such a crystal may be, for example, about 0.5 mm to about 1 mmthick, which is much less than traditional lenses that act by physicallyrefracting light waves. Light collimating photonic crystals may includephotonic structures etched in very thin vapor deposited films. The useof photonic crystals further minimizes the thickness of the distal headend of the device. Although not required, the use of photonic crystalsand implementation of direct mounting of LED dies to body 102′ (or thebody of any of the other described embodiments) rather than using an LEDpackage assembly together works to further minimize the overallstructure of the device, for example, allowing for a very thin distalhead end that is more maneuverable within the patient's mouth.

The LED dies themselves used with any of the described embodiments maycomprise any suitable LEDs configured to emit within the desiredspectrum. Exemplary LED dies include inorganic solid-state LED dies andorganic LED dies. Organic LED (OLED) dies are light emitting diodeswhose emissive electroluminescent layer includes a film of organiccompounds. The layer may typically include a polymer that allowssuitable organic compounds to be deposited. The organic compounds aredeposited in rows and columns onto a flat carrier. The use of OLED diesmay further reduce the thickness of the distal head portion of thedental curing light, as OLED dies are flexible and thinner thanconventional inorganic solid-state LED dies (e.g., the use of OLED diesalone may reduce thickness by 1-2 mm).

For example, the distal head end of any of the disclosed embodiments mayhave a thickness less than about 8 mm. More particularly embodimentsincluding direct LED mounted dies, OLEDs, and/or a photonic crystal forlight collimation rather than a lens may also have a thickness less thanabout 8 mm, more preferably less than about 5 mm, even more preferablyless than about 2 mm (e.g., as thin as about 1 mm or less).

FIG. 5C shows a cross-sectional view of a dental curing light that mayotherwise be similar to that of FIG. 5B, but in which the neck 108″ andhead portions 110″ are differently shaped, maximizing benefitsassociated with the thinness of the distal head portion 110″. Forexample, a top surface of the body along the transition from the neck108″ to distal head portion 110″ is substantially straight and flat,while the underside of the body includes a curvature to transition fromthe neck portion 108″ to the thinnest portion of the device, the distalhead 110″. The proximal grippable handle portion (not shown) may beshaped and sized similarly to the embodiment shown in FIG. 1, as thehandle portion is the widest portion of the device, configured forgripping. Providing a flat top surface throughout neck portion 108″ andhead portion 110″ may maximize maneuverability within the mouth,although alternative configurations may include a flat bottom surface orbe curved on both top and bottom surfaces. Head thickness T may be lessthan about 8 mm, more preferably less than about 5 mm, more preferablyless than about 2 mm, or even less than about 1 mm. Of course, use ofthe above described photonic crystal light collimators, direct mountingof LED dies, as well as the use of OLED dies is not limited to theembodiment described in conjunction with FIGS. 5B-5J, but such featuresmay be used with any of the dental curing lights described herein.

In embodiments where at least one LED die is configured to emit a firstpeak wavelength (e.g., UV at about 390-410 nm) and another LED die isconfigured to emit a different peak wavelength (e.g., blue at about440-480 nm), more than one photonic crystal may be required, as eachcrystal is customized for a particular peak wavelength. Exemplaryphotonic crystals may be available from ePIXnet, located in St. Andrews,United Kingdom; Luminus Devices, Inc., located in Billerica, Mass.;Obducat AB, located in Malmo, Sweden, and Daylight Solutions, Inc.,located in Poway, Calif.

As illustrated, the device 100′ may further include a reflective well168′ within which the LED dies 160′ are disposed. Reflective well 168′may further aid in redirection of any emitted light (e.g., not capturedby photonic crystal 150′ or in embodiments not including crystal 150′)in a desired direction. A transparent protective layer 161′ (e.g.,silicone) may be applied over structures 160′ and 150′ so as to protectthem from being damaged by rough handling or dropping during use. Anyfeatures described in conjunction with the embodiments of FIGS. 5B-5Jcould be adapted for use with any of the other embodiments describedherein. For example, one embodiment may include direct mounted LED dieson a separate LED head assembly that is receivable into an LED headassembly hole of the unitary body.

According to one method of manufacture, a unitary single piece metallicbody 102′ is provided, as shown in FIG. 5D. As shown in FIGS. 5E-5F, athin electrically insulative and thermally conductive layer 154′ isformed over at least the distal head end exterior surface of the metalbody 102′. The thin layer 154′ preferably comprises an oxide or nitrideof the underlying metal body material 102′ (e.g., in embodiments wherebody 102′ is metallic). It may be applied by chemical or plasma vapordeposition, plasma flame spraying, or other techniques that will beapparent to those skilled in the art. Conductive traces 170′ may beapplied so as to be sandwiched between the electricallyinsulative/thermally conductive layer 154′.

As shown in FIGS. 5G-5H, one or more LED dies 160′ are then laid downand bonded directly to an exterior surface of the thin electricallyinsulative/thermally conductive layer 154′, for example, with athermally conductive epoxy. The thickness of any such epoxy layer isminimized so as to be extremely thin so that its effect on resistance tothermal conductivity is negligible, as thermally conductive thermalepoxies, although characterized as thermally conductive, are stillrelatively poor thermal conductors (e.g., perhaps as little as 1 W/m-K).Minimization of the thickness of any such layer minimizes its negativeeffect on heat dissipation. Photonic crystals 150′ may be attached overLED dies 160′ so as to receive emitted light.

As shown in FIG. 5I, a reflective well 168′ may be attached to thedistal head end 110′ of body 102′ such that dies 160′ are enclosedwithin reflective well 168′. Although it may be possible to installreflective well 168′ prior to mounting dies 160′, it is preferred tomount dies 160′ on a completely flat, smooth surface to ensure goodcontact with the power connections 171′ and underlying thermallyconductive/electrically insulative layer 154′. Accordingly, reflectivewell 168′ is preferably attached at a later stage. Finally, as shown inFIG. 5J, a silicone or other hardenable or curable resin protectivecoating may be applied over dies 160′ and photonic crystals 150′ so asto protect these delicate structures from damage. Additional details ofembodiments including direct mounted LED dies may be found in U.S.Patent Application Ser. No. 61/141,482 filed Dec. 30, 2008, previouslyincorporated by reference.

The dental curing device can have any shape suitable for use as a curingdevice. In one embodiment, the dental curing device can have an elongateshaped body to facilitate use of the device in the mouth of a patient.An elongate shape of the dental curing device is but one example of adental curing light within the scope of the invention. It will beappreciated that the dental curing light may have other shapes suitablefor use in curing a dental composition within, or even outside, apatient's mouth. For example, curing lights known in the art having agun-like configuration may incorporate any of the features disclosedherein. In general, any known curing light configuration may be used inconnection with the features described herein.

Because the device body serves as a heat dissipater, there is norequirement for a cavity, opening, or other configuration of the devicebody to accommodate a separate metal body thermally coupled to the LEDwith sufficient heat capacity to function as a heat sink. The ability toremove the “traditional heat sink” from the dental curing light devicesdescribed herein allows for a low profile dental curing light device tobe manufactured. In particular, the neck and head portions can be mademuch smaller and/or thinner and/or accommodate larger LED assembliescompared to dental curing lights that use a separate heat sink housedwithin the head or neck portions of the curing light devices. Anembodiment including an extremely thin distal head is shown in FIG. 5C.

Because device body 102 comprises a thermally conductive material, itcan serve as a heat conductor and dissipater. Furthermore, the devicebody 102 can be made more solid and thinner as compared to the housingof plastic body dental curing lights. In one embodiment, the thermallyconductive body material is of a metal construction that providesincreased strength and durability while still achieving a smaller, moremaneuverable curing light.

In one embodiment, the handle portion of the device body can have athickness in a range from about 10-40 mm, more preferably about 15-30mm. Such dimensions provide for comfortable gripping by the user. Theneck and head portions are thinner than the handle portion and can havea thickness in a range from about 1-15 mm, more preferably about 1-10mm. As described above, a head portion thickness less than about 8 mm,more preferably less than about 5 mm, or even less than about 2 mm maybe possible when using one or more of direct die mounting, photoniccrystal light collimation, or organic LEDs.

B. Protective Coating

In one embodiment, all or a portion of the exterior surface of thedevice body includes one or more coatings. For purposes of thisinvention, the exterior surface of device body 102 is the surface thatis exposed in the assembled curing light or covered by a coating layerthat does not substantially change the shape of the surface. Forexample, in the embodiment illustrated in FIGS. 1-5, the surface of neckportion 108 is an exterior surface, but the surface of interior cavity136 is not an exterior surface since electronics assembly 112 covers upthe surface. Similarly collar 140 as illustrated in FIGS. 1-5 is not anexterior surface since it is covered by protective sleeve 118. However,if desired, portions of device body 102 that do not provide an exteriorsurface may be coated.

The exterior surface of device body 102 may be coated with one or morecoatings to protect the surface and/or to facilitate cleaning and/orsterilizing the curing light 100. In one embodiment, the exteriorsurface of device body 102 may be coated with a scratch resistantcoating and/or a fluoropolymer coating. FIG. 6 is a cutaway view of aportion of the neck portion 108 of device body 102 illustrating aprotective coating. A scratch resistant coating 146 is positionedadjacent the surface of device body 102. The coating layers may beapplied by chemical or plasma vapor deposition, plasma flame spraying,or other techniques that will be apparent to those skilled in the art.

Scratch resistant coating 146 can be a thin layer of any material thathas a hardness greater than the body material of device body 102. In oneembodiment, the scratch resistant layer can be a metal oxide or a metalnitride. The scratch resistant layer may be the same as the thermallyconductive layer. In one embodiment, the scratch resistant coating 146can be an anodized layer formed on the surface of a metallic device body102. For example, where the metallic body material includes aluminum,anodizing the surface of the device body 102 creates an aluminum oxidesurface. In a preferred embodiment, the scratch resistant coating 146 isbetween about 0.05 micron to about 100 microns thick (not shown to scalein FIG. 6). Preferably the thickness is greater than about 1 micron,more preferably greater than about 10 microns, and most preferablygreater than about 25 microns. In one embodiment, the thickness can bein a range from about 1 micron to about 40 microns or, alternatively, ina range from about 5 microns to about 50 microns.

While the thickness of the scratch resistant layer can depend somewhaton the material being used and the desired scratch resistance, foranodized aluminum, the thickness of the scratch resistant layer must besubstantially greater than about 5-15 nm, which is the thickness ofself-passivated aluminum, which is known to not have a thicknesssufficient for imparting scratch resistance.

In a preferred embodiment, the hardness of the scratch resistant coatingis greater than about 55, more preferably greater than about 60, andmost preferably greater than about 65 on the Rockwell C scale. Thehardness is typically in a range from about 60-90, more preferably about65-80 on the Rockwell C scale. Examples of suitable scratch resistantcoatings include aluminum oxide, aluminum nitride, chrome nitride,chrome oxide, zirconium oxide, titanium nitride, tungsten carbide,silicon carbide, chrome carbide, and combinations thereof.

The fluoropolymer coating 148 that may be applied to an exterior surfaceof the device body can provide a surface that minimizes friction so asto render device highly maneuverable within the mouth. Furthermore, thedevice is easily sterilized and less prone to retain bacteria and/ordebris, which is important since the dental curing light is used in themouth of a dental patient and must be cleaned between uses to avoidcontamination and infection between dental patients. In one embodiment,the fluoropolymer coating has a thickness in a range from about 0.05micron to about 10 microns, more preferably about 0.1 micron to about 1micron. Examples of suitable fluoropolymers include, but are not limitedto, polytetrafluoroethylene, perfluoroalkoxy polymer, fluorinatedethylene-propylene, polyethylenetetrafluoroethylene,polyethylenechlorotrifluoroethylene, polyvinylidene fluoride,polychlorotrifluoroethylene, and combinations of these. Although perhapsnot technically a fluoropolymer, a parylene coating (e.g., applied bychemical vapor deposition) may additionally or alternatively be applied.Parylene is a polymer manufactured from di-p-xylylene. It can be appliedin a thin, clear layer, and is biocompatible. As used herein,“fluoropolymer coating” is to be broadly construed to also includeparylene coatings. Parylene coatings may include Parylene N, Parylene C,Parylene D, Parylene AF-4, Parylene SF, Parylene HT, Parylene A,Parylene AM, Parylene VT-4, Parylene CF, and Parylene X.

The fluoropolymer coating 148 may be used alone or in combination withthe scratch resistant coating 146. However, the use of a scratchresistant coating 146 under fluoropolymer coating 148 has been found toprovide substantial benefits that cannot be achieved by either layeralone. For example, fluoropolymer coating 148 can be difficult to bondto some metallic surfaces. In one embodiment, the scratch resistantcoating 146 is selected to provide good adhesion of the fluoropolymercoating 148 to the exterior surface of device body 102. For example,metal oxides such as aluminum oxide provide good bonding betweenaluminum alloys and fluoropolymers such as polytetrafluoroethylene.

The scratch resistant coating 146 can also prevent abrasion offluoropolymer coating 148, even in embodiments where the scratchresistant coating is positioned below the fluoropolymer coating. Thehardness of the scratch resistant coating helps to prevent the formationof dents within the body material, so that the exterior surface remainssmooth, and objects or materials contacting the fluoropolymer surfacewill slide off the surface without substantially abrading the surface.If a scratch, dent, or other defect were to develop on the surface ofthe device body, the fluoropolymer coating may be more easily abraded atthe edge of the defect. The inclusion of the scratch resistant coating146 helps to prevent this from occurring. The scratch resistant coatingand/or the fluoropolymer coating may each comprise a single layer or oneor both may include two or more sublayers.

C. Head Portion Including LED and Thermally Conductive Layer

In one embodiment, the head portion 110 of device body 102 includes anLED assembly 120 that allows a dental practitioner to illuminate apolymerizable composition and cause the polymerizable composition tocure. FIG. 7 is a partial cutaway view of dental curing light 100illustrating the distal end portion 104 in greater detail. Head portion110 supports or contains LED assembly 120. LED assembly 120 may includea lens 150, an LED package 152, and a thermally conductive layer 154. Inthe embodiment of FIG. 7, thermally conductive layer may comprise aseparate, relatively thick member that is secured to body 102, ratherthan being a very thin layer applied by vapor deposition or plasma flamespraying techniques, as that shown in FIGS. 5B and 5D-5J. Of course, analternative in which a relatively thin thermally conductive layer isapplied to body 102 (e.g., by vapor deposition or plasma flame spraying)is possible.

LED package 152 and thermally conductive layer 154 are disposed withincavity 144. Wires 134 and 134 b extend through passageway 142 andprovide power to LED package 152. LED package 152 and thermallyconductive layer 154 are secured to the floor 156 of cavity 144. Floor156 is typically flat to facilitate good contact between thermallyconductive layer 154 and the surface of floor 156. However, otherconfigurations can be used so long as the surface area in contactbetween the device body 102 and the thermally conductive layer 154 issufficient to quickly conduct the heat produced by the one or more LEDdies through thermally conductive layer 154 during use. Thermallyconductive layer 154 can be thermally coupled, bonded, or otherwisesecured to floor 156 using any technique that ensures good thermalcontact. Thermally conductive layer 154 is thermally coupled to LEDpackage 152 through LED assembly substrate 162, which may be part ofpackage body 164, which is described more fully below with reference toFIGS. 7-8.

The thermally conductive layer 154 includes at least a first layer of ahighly thermally conductive material. The thermal conductance of thefirst layer material is preferably greater than about 150 W/m-K, morepreferably greater than 170 W/m-K, even more preferably greater than 200W/m-K, and most preferably greater than about 300 W/m-K. In oneembodiment the conductivity can be in a range from about 150 W/m-K toabout 2000 W/m-K, more preferably about 170 W/m-K to about 500 W/m-K.Examples of first layer materials that may be used to make thermallyconductive layer 154 include, but are not limited to, aluminum nitride,beryllium oxide, diamond, silicon carbide, boron nitride, nanomaterialsof carbon (e.g., carbon fiber, carbon nanotube fiber, and/or graphene),beryllium oxide, boron nitride, and/or other thermally conductiveceramics and/or thermally conductive particulate metals and/or ceramicsand/or derivatives thereof and/or combinations thereof.

In one embodiment, the first layer of the thermally conductive layer 154is not electrically conductive. The use of non-electrically conductivematerials in the first layer allows the thermally conductive layer toinclude traces. The traces can be patterned to electrically couple tothe contacts of the LED assembly substrate to provide power to the LEDdies. The traces can be made from any material useful for making traces,such as, but not limited to, gold, copper, silver, platinum, oraluminum. In one embodiment, the traces can be provided by a copper pador plate.

In one embodiment, the first layer of the thermally conductive layer 154is made of a material that has a coefficient of thermal expansion thatis substantially matched to a coefficient of thermal expansion of theLED assembly substrate 162.

In one embodiment the thermally conductive layer can be a thermallyconductive printed circuit board. The thermally conductive printedcircuit board can be a ceramic circuit board or a metalized printedcircuit board. Those skilled in the art of circuit boards are familiarwith techniques for manufacturing thermally conductive printed circuitboards.

In one embodiment, the thermally conductive layer can include adeformable layer such as a thermally conductive deformable pad and/or athermally conductive gel or grease layer. Typically the deformable layeris positioned below the first layer (i.e., adjacent the device body).Examples of thermally conductive greases include silicon greases,polymer greases, metalized greases, and nanoparticle greases.Nano-particle greases typically include a thermally conductive filler(e.g., ceramic, carbon, or diamond).

Examples of thermal gels are available from the following companies atthe following website, the content of which is hereby incorporatedherein by reference:

ShinEtsu: http://www.microsi.com/packaging/thermal_gel.htm AiTTechnology: http://www.aitechnology.com/products/thermalinterface/thermgel/ Ultra+5: http://www.tigerdirect.com/applications/SearchTools/item-details.asp?EdpNo=3298395&CatId=503 Masscool ThermalGel: http://www.tigerdirect.com/applications/searchtools/item-details.asp?EdpNo=480215&csid=_21

The thermally conductive grease, gel, or adhesive can include a fillermaterial to improve thermal conductivity. Examples of thermallyconductive filler materials include aluminum nitride, beryllium oxide,carbon, diamond, silicon carbide, boron nitride, and combinations ofthese and/or nanomaterials thereof. In some embodiments, a separatethermally conductive layer 154 may not be required. For example,depending on the characteristics of the LED assembly and the LEDassembly substrate 162 included therein, no additional thermallyconductive layer 154 may be required. In such an example, the LEDassembly substrate 162 effectively serves as a sufficient thermallyconductive layer, and may simply be coupled to the underlying body ofthe dental curing light with a thermally conductive grease, gel, oradhesive. Such LED assembly substrates 162 would preferably have surfacearea and thickness characteristics similar to the characteristicsdescribed herein relative to a separately employed thermally conductivelayer 154.

In a preferred embodiment, the thermally conductive layer 154 has ahigher thermal conductivity than the thermal conductivity of thematerial used in the device body (e.g., the material that forms thesurface of floor 156, for example an aluminum alloy).

The thermally conductive layer 154 is thin relative to body 102 andtherefore lacks sufficient mass and heat capacity to serve as a heatsink. In one embodiment, the thickness of the thermally conductive layer154 is in a range from about 100 microns to 1.5 mm, more preferablyabout 200 microns to about 1 mm and most preferably about 500 microns to900 microns. The thickness of such layer 154 is significantly greaterthan embodiments in which the thermally conductive layer comprises alayer applied by vapor deposition or plasma flame spraying techniques.For example, such layers may only have a thickness between about 0.05micron and about 50 microns. In any case, the thermal conductivity ofthe layer 154 is sufficiently high that the thermally conductive layer154 serves as a conduit to dissipate heat from the one or more LED diesto the material of the device body. In this manner, the material of thedevice body can serve as a highly efficient heat dissipater. The surfacearea coupling the thermally conductive layer to the device body issufficiently large that a majority of heat being conducted by thethermally conductive layer is transferred to the device body.

The thermally conductive layer 154 is thermally coupled to the LEDpackage 152 and the device body 102. The thermal coupling of thethermally conductive layer 154 to the LED package 152 and the devicebody 102, in combination with the thickness of the thermally conductivelayer, can be selected to ensure that most, if not essentially all, theheat generated by the LED dies during use of the curing light 100 isquickly conducted into the body material for dissipation. Because theconfiguration is so efficient at conducting heat away from the LED dies,low to moderate temperatures are maintained, even during continuousoperation.

In a preferred embodiment, layer 154 has substantially more contactableplanar surface area than package 152. Oversizing the thermallyconductive layer 154 can significantly improve heat dissipation bytransferring heat to the device body around the periphery of LED package152. The use of the device body as a heat dissipater allows amplesurface area in which the thermally conductive layer can transfer heatat a significant rate from the LED package 152. Thus, the thermallyconductive layer utilizes the heat capacity of the device body muchbetter than directly coupling the LED package 152 to the device body. Ingeneral, because the thermally conductive layer 154 has a higher thermalconductivity than the device body, the larger the surface area couplingthe thermally conductive layer 154 and the device body 102, the greaterthe rate of heat transfer to the device body.

The use of a thermally conductive layer in contact with sufficientsurface area of a device body has been found to provide surprisinglygood heat dissipation from the LED package. The configuration used inthe present invention essentially obviates the long existing problemsassociated with over-heating in LED-based curing lights.

As mentioned, the thermally conductive layer 154 can have a thermalconductivity that is greater than that of the device body. In oneembodiment, the thermally conductive layer 154 has a higher thermalconductivity than aluminum alloys. While the device body can be madefrom several different materials, aluminum alloys have been found toprovide a good balance between heat capacity/thermal conductivity andmanufacturability and durability of the device body. Although aluminumalloys tend to have poorer heat transfer characteristics than purealuminum, the thermally conductive layer provides quick dissipation to asufficiently large area of the aluminum alloy to overcome thedisadvantages of using aluminum alloys compared to pure aluminum. Thisis a surprising and unexpected result.

As shown in FIG. 7, curing light 100 may include a focusing lens 150used to focus the light generated by LED package 152. The focusing lens150 can be any lens suitable for collimating light with the wavelengthsand light intensities utilized in the dental curing light 100. WhileFIG. 7 illustrates a traditional refractive lens configuration, thepresent invention may include other types of lenses, including photoniccrystals for light collimation.

In one embodiment, assembly 120 includes the one or more LED dies in apackage. Any LED package suitable for use in curing polymerizablecompositions that can be coupled to a thermally conductive layer, andthereby coupled to the device body 102, can be used in the presentinvention. Moreover, two or more LED packages having one or moreadditional LED dies emitting at the same or a different wavelength canbe used in the dental curing lights of the present invention. Anexemplary LED package 152 is illustrated in FIGS. 8-9. LED package 152includes an LED die 160 that is mounted on an assembly substrate 162 ofpackage body 164. Assembly substrate can be used alone or in combinationwith any other features of an LED package. For example, in thenon-limiting example shown in FIGS. 7 and 8, package body 164 surroundsLED die 160 and forms a package cavity 166 having a floor 167. Packagecavity 166 typically has a slanted wall 168. Wall 168 and/or othersurfaces of package 152 can be coated with a reflective coating to limitabsorption of light generated by LED die 160 and maximize light output.In addition, the same or a different reflective coating can be appliedto internal surfaces of head cavity 144 and head 110 to minimizeabsorption of light from LED die 160. Examples of suitable reflectivematerials include, but are not limited to, noble metals, preferablyrhodium. In one embodiment, package 152 can have a reflective collarand/or an antireflective coating similar to the collar andanti-reflective coating described below in conjunction with FIG. 13.

LED assembly substrate 162 can comprise any material suitable forsupporting LED die 160, so long as substrate 162 has a sufficiently highthermal conductivity to transfer heat from die 160 to thermallyconductive layer 154 (FIG. 7). In one embodiment, substrate 162 can beformed of the same or a similar material as the first layer of thermallyconductive layer 154. LED assembly substrate can be made from one ormore sublayers and can be made from one or more different thermallyconductive materials so long as the desired thermal conductivity ismaintained. LED die 160 can be provided as a prepackaged LED package oralternatively, the LED package can be created in-situ on the devicebody.

The LED dies are selected to emit at a desired wavelength for curing apolymerizable composition. The LED die is typically configured to emitat a particular wavelength within the range from about 350 nm to about490 nm, although the invention is not necessarily limited to devicesthat emit at these wavelengths. Light curable dental compositionstypically include light activated initiators that only respond to a verynarrow range of wavelengths. For example camphorquinone is activated byblue light, while many proprietary initiators are activated by UV light.LED dies that are selected to operate at the desired wavelength areimportant for achieving curing in the desired manner and time intervalfor the particular polymerizable composition. In one embodiment, the LEDpackage can have one or more LED dies configured to emit light at aparticular frequency in a range from about 350 nm to about 490 nm. In apreferred embodiment, the LED package can emit light at least in the UVspectrum and separately or simultaneously in the blue spectrum. Examplesof suitable LED packages and dies that can be used in the dental curinglights of the present invention are disclosed in U.S. Pat. No. 7,473,933to Yan, which is hereby incorporated herein by reference.

Power connections to the LED die 160 can be made through contacts 170 aand 170 b. In this embodiment, the contacts may be embedded in substrate162. However, in other embodiments, contacts may be placed in otherstructures of the package body or other components of the LED assembly.Contacts and traces to LED die 160 may be made from gold or otherconductive metal traces deposited using known techniques such as, butnot limited to, deposition techniques. While LED package 152 has beenillustrated as receiving power from wires 134 a and 134 b, power can besupplied using traces or leads or any other technique suitable fordelivering power to the LED die. In one embodiment, traces to LEDpackage 152 can be embedded in an electrically insulative coating suchas the scratch resistant coating or an applied thermally conductivelayer as described in conjunction with FIGS. 5B and 5D-5J. In thisembodiment, the electrical contact (e.g., wires or traces) between head110 and cavity 136 can travel along the outside of neck portion 108 ofdevice body 102. The wires or traces can be embedded in the coating byusing a first electrically insulating layer such as aluminum oxidebeneath the traces and then another electrically insulating coatinglayer such as aluminum oxide above the traces. The insulating coatinglayers can be aluminum oxide, aluminum nitride or any other suitableelectrically insulating coating. The lower insulating layer can beformed by anodizing an aluminum body and the upper insulating layer canbe formed by plasma flame spraying.

FIG. 10 illustrates an alternative embodiment of the invention includinga plurality of LED dies 260 a, 260 b, 260 c, and 260 d. The use ofmultiple dies allows the package 252 to emit at more than one wavelengthand/or emit more light at one wavelength. In one exemplary embodiment,LED dies 260 a and 260 b are configured to emit light in a range fromabout 460 nm to about 470 nm, die 260 c is configured to emit light in arange from about 445 nm to about 455 nm, and die 260 d is configured toemit light in a range from about 400 nm to about 410 nm (e.g., about 405nm). LED package 252 can include any number of dies so long as there isphysical space available for the die footprint. The LED dies may beconfigured to emit light at any frequency suitable for curing a lightpolymerizable composition. LED package 252 includes contacts 270 a-270 cfor driving LED package. The LED dies can be driven in series orparallel and at voltages and power outputs similar to those discussedwith respect to FIGS. 1-9.

D. Alternative Dental Curing Lights

FIGS. 11-13 illustrate an alternative dental curing light 200 thatincludes a head portion having a removable cup-like member 280.Removable member 280 houses an LED package 252 that is coupled toremovable member 280 using a thermally conductive layer 254. The thermalconductance between LED package and device body 202 is the same as forcuring light 100 except that head 210 includes coupling means forsecuring member 280 to a part of head 210.

In one embodiment, the coupling is provided by a threaded body 282 andthreads 284 on member 280 allows removable member 280 to be screwed intothreaded body 282 of head 210. A floor 256 of well or cavity 244 is inintimate contact with a bottom surface 286 of removable member 280. Therelatively large surface area of bottom 286 of removable member 280 andfloor 256 of cavity 244 ensure good heat transfer between the parts ofhead 210. The connection between removable member 280 and cavity 244 canbe made using any removable connection such as, but not limited to,threads, a snap fit connection, pin connector, or similar connectionthat provides a similar functionality.

Removable member 280 can be made from the same materials as the otherparts of device body 202 as described above with respect to device body102. In one embodiment, removable member 280 is made from the samematerial as device body 202. However, in an alternative embodiment,removable member 280 may comprise a metal or other thermally conductivematerial that has higher thermal conductivity compared to the otherparts of device body 202.

The electrical connection between wires 234 and LED package 252 may beaccomplished by providing a pair of spring loaded contacts 290 a and 290b. Removable member 280 includes corresponding electrical contacts 292 aand 292 b that compress spring loaded contacts 290 a and 290 b asremovable member 280 is screwed down. Any electrical coupling means canbe used so long as electrical contact can be made with removable member280 securely seated in cavity 244.

The use of a removable member 280 allows LED package 252 to berelatively easily replaced or upgraded. To replace or upgrade the LEDpackage 252 with a repaired or improved LED package, the removablemember 280 can be removed and a new removable member 280 including a newLED package 252 can be screwed into or coupled onto head 210. Dentalpractitioners can thereby avoid the expense of returning the entiredevice to a manufacturer (as in the case of a broken device) ordiscarding the entire device when a newer device is desired. Removablemember 280 can be used in combination with any of the features describedabove with regard to any of the disclosed curing lights.

FIG. 13 also illustrates a reflective collar 294 that defines an openinghaving an interior surface 295. Reflective collar 294 reflects andchannels light from LED package 252 to lens 250. In a preferredembodiment, reflective collar 294 has a cylindrical shape; however, ifdesired, other shapes may be used. Reflective collar 294 may include areflective coating on interior surface 296 that improves thereflectivity of light on the surface thereof, thereby reducingabsorption. The reflective coating is preferably a high sheen noblemetal coating. Rhodium and palladium are examples of suitable noblemetals and rhodium is particularly preferred. Noble metals are preferredfor their ability to resist tarnishing, which can reduce reflectivityover time.

In one embodiment, the components of removable member 280 can be securedusing a snap fit 298 created between a portion of lens housing 300 andthreaded body 282. Reflective collar 294 can be secured within removablemember 280 by wave spring 302 that abuts first washer 304, which alsoabuts lens housing 300. A second washer 306 separates reflective collar294 from the bottom of removable member 280. The reflective collar 294can be secured using a different type of spring, or with a differenttype of connection mechanism, such as, but not limited to, an adhesive.

In one embodiment, lens 250 has an antireflective coating on the surfacethereof. The anti-reflective coating is preferably on the surface facingthe LED dies; however, other surfaces can also be coated. Theanti-reflective coating reduces reflection of the light off the surfaceof the lens, thereby increasing the percentage of light that passesthrough lens 250 and reduces absorption caused by light reflected offlens 250. Examples of anti-reflective coatings include, but are notlimited to, magnesium fluoride. Of course, one or more collimatingphotonic crystals may be used as an alternative to lens 250.

The foregoing structures and coatings shown with respect to theembodiment of FIG. 13 can be used in combination with the featuresdescribed in FIGS. 1-10 above.

In another alternative embodiment of the invention, the dental curinglight includes a rechargeable battery in the cavity of the handleportion of the device body. In this embodiment, an electrical plug orother connection at the proximal end of the handle portion replaces thepower cord and allows the dental curing light to be connected to acharging station or base for recharging the battery. Underpowering theLED package as described above is particularly advantageous when used incombination with a rechargeable battery to allow higher power output fora longer period of time without recharging and/or to reduce the size ofthe battery pack while achieving desired periods of use betweenrecharging.

III. Operating Configurations of Dental Curing Lights and Methods of Use

The dental curing lights of the present invention can be configured toemit at very high light output and/or to emit continuously at lowoperating temperatures and high efficiencies. In one embodiment, thecuring light device includes an electronics assembly that controls powerto the LED package. The electronics assembly can be configured to drivethe LED die at very high light intensities for extended periods of timewithout overheating the LED die.

In one embodiment, the LED package can produce stable emission of totallight output of at least about 2000 mW/cm², at least 3000 mW/cm², oreven greater than 3500 mW/cm². For purposes of the present invention,unless otherwise indicated, total light output is measured using athermopile measurement device. Other types of light measuring devicesthat can be used in some embodiments include spectrometers and DemetronRadiometers.

The LED curing devices of the present invention can achieve stable lightoutput with an LED that is as intense as or even more intense than lightgenerated by an arc lamp, which typically operates at 3500 mW/cm². Theability to emit light at such high light outputs using an LED lightsource is due in part to the use of the device body as a heat dissipaterand the use of the thermally conductive layer to quickly and efficientlyconduct the head away from the LED dies to the device body, where theheat is dissipated.

In one embodiment of the invention, the electronics assembly isconfigured to minimize wavelength shifting of the output of the LEDdies, even at high intensity output. In this embodiment, the electronicsassembly is configured to power the LED dies at a maximum input powerthat is substantially below the actual maximum or rated power of the LEDdies. For example, the curing light can include one or more LED diesthat are rated for operation at about 10 watts and the electronicsassembly can be configured to power the device at a maximum input powerof about 2.5 Watts.

In one embodiment, the electronics assembly is configured to power theLED package at a maximum input power of less than 80% of the ratedmaximum power of the LED dies, more preferably less than about 50%, evenmore preferably less than about 40%, and most preferably less than about30% of rated maximum power, while achieving a light output of at leastabout 500 mW/cm², more preferably at least about 800 mW/cm², morepreferably at least about 1000 mW/cm², even more preferably at leastabout 2000 mW/cm², or even at least about 3000 mW/cm².

In one embodiment, the LED curing light can be configured to have a veryhigh efficiency of total light output per watt of power input, even athigh light output. The devices of the invention can be configured tohave an efficiency of total light output that is significantly greaterthan the typical efficiencies in high powered curing lights previouslyknown, which tend to have efficiencies of total light output per watt ofinput power in the 10%-30% range. In one embodiment, the efficiency ofthe LED dies of the curing light of the invention is at least about 40%,more preferably at least about 50%, even more preferably at least about60% and most preferably at least about 70%, where the efficiency ismeasured according to the watts of total light output from the curinglight per watt of input power to the LED dies. For example in oneembodiment, a curing light having an LED package with 4 LED dies and arated power of 10 watts is operated at 6 watts and outputs a total lightintensity of 3500 mW/cm². The highest efficiencies of the dental curinglight device may be achieved with configurations including a reflectivecollar between the LED and the lens or photonic crystal. The use of ananti-reflective coating on any employed lens further improvesefficiency.

Driving the LED dies at a fraction of their rated maximum powerminimizes temperature cycling of the LED dies and nearby structure. Thistechnique is particularly advantageous for use with LED configurationsthat include two or more LED dies. Driving a first LED die below itsrated power ensures that the adjacent LED die emits at its designwavelength at a desired power output. Thus, a plurality of LED dies canbe simultaneously operated at one or more desired wavelengthscontinuously for an extended period of time without causing detrimentalwavelength shift or significant power drop in any of the LED dies as aresult of overheating.

Underdriving the LED package results in reduced operating temperaturesnear the LED die. In one embodiment, the temperature in the LED packageadjacent the dies can be kept below about 80° C., more preferably belowabout 70° C., and most preferably below about 50° C., which is muchcooler than the typical maximum operating temperatures (e.g., more than125° C.) of traditional curing light systems. The cool running curinglights of the invention can be inserted into the mouth of the dentalpatient without fear of burning the patient or causing discomfort.Although some embodiments of the invention include underdriven LED dies,in other embodiments it may be desirable to overdrive the LED to producea shift in wavelength.

In one embodiment of the invention, the power input and light output ofthe dental curing light 100 can be ramped over a period of time. The lowoperating temperature and/or high light output of the curing lights ofthe present invention provides for many possible ramp times and lightoutput intensities. A ramp time may be appropriate for one scenario butnot for another. In one embodiment, the dental curing light may includecircuitry configured to allow the user to choose a ramp time for rampingup the light output of the dental curing device. In one embodiment, anelectronics assembly of the dental curing device includes a plurality ofselectable ramp times within a range from about 2-20 seconds, morepreferably 5-15 seconds. Exemplary selectable times include 5 seconds,10 seconds, 15 seconds, and 20 seconds. In this embodiment, the userselects one of the plurality of ramp times and the device incrementallyincreases power input to reach the selected light output intensity inthe selected period of time. For example, if the selected lightintensity output is 2000 mW/cm² and the user selected ramp time is 5seconds, the electronics assembly incrementally increases power input tothe LED die to reach a light intensity output of 2000 mW/cm² within 5seconds. Using the same device, the user can select a different ramptime, such as 3 seconds, and the electronics assembly will incrementallyincrease input power to the desired light intensity output (e.g., 2000mW/cm²) within 3 seconds. Additional details regarding ramping aredescribed in U.S. Patent Publication No. 2006/0033052 to Scott, which ishereby incorporated herein by reference.

The present invention also includes methods of curing a polymerizablecomposition using a dental curing light. The method includes (i)providing a dental curing light according to one or more of theforegoing embodiments, (ii) depositing a light curable compositionwithin the oral cavity of a patient, and (iii) curing the compositionusing the dental curing light by directing a beam of light toward thepolymerizable composition for a sufficient amount of time to cure thelight curable composition, the beam of light having a light intensity ofat least about 2000 mW/cm². The dental composition includes apolymerizable component and a photo initiator that is sensitive to lightat the wavelength emitted from the light curing device. Examples oflight curable dental compositions are disclosed in U.S. PatentPublication No. 2006/0194172 to Loveridge, which is hereby incorporatedherein by reference. Those skilled in the art are familiar withwavelengths and compositions for placing and curing a curablecomposition in the tooth of a patient.

It will be appreciated that the present claimed invention may beembodied in other specific forms without departing from its spirit oressential characteristics. The described embodiments are to beconsidered in all respects only as illustrative, not restrictive. Thescope of the invention is, therefore, indicated by the appended claimsrather than by the foregoing description. All changes that come withinthe meaning and range of equivalency of the claims are to be embracedwithin their scope.

1. A dental curing light device having a thermally conductive layer fordissipating heat from an LED, comprising: a device body having aproximal end and a distal end, the device body being formed of athermally conductive body material, the device body including a headportion, the head portion configured to support or contain an LED; anLED assembly thermally coupled to the head portion of the device body,the LED assembly including one or more LED dies and a thermallyconductive LED assembly substrate, the one or more LED dies beingelectrically coupled to one or more contacts on the LED assembly, theone or more LED dies being configured to emit a spectrum of lightcapable of curing a light curable composition; and a thermallyconductive layer that thermally couples the LED assembly with the devicebody, wherein a surface area coupling the thermally conductive layerwith the device body is sufficient to conduct away a majority of wasteheat generated by the one or more LED dies with the light curing deviceset to a highest power setting.
 2. A dental curing light device asrecited in claim 1, wherein a surface area coupling the thermallyconductive layer with the device body is about as large or larger than asurface area coupling the thermally conductive layer with the LEDassembly substrate.
 3. A dental curing light device as recited in claim1, wherein a surface area coupling the thermally conductive layer withthe device body is at least about 10% larger than a surface areacoupling the thermally conductive layer with the LED assembly substrate.4. A dental curing light device as in claim 1, further comprisingelectrical circuitry configured to drive the one or more LED dies to anoutput light intensity of at least about 500 mW/cm².
 5. A dental curinglight device as in claim 1, further comprising electrical circuitryconfigured to drive the one or more LED dies to an output lightintensity of at least about 2000 mW/cm².
 6. A dental curing light deviceas in claim 1, further comprising electrical circuitry configured todrive the one or more LED dies with a maximum input power that is lessthan about 70% of a rated maximum power of the LED die while achieving aluminescence of at least about 800 mW/cm².
 7. A dental curing lightdevice as in claim 1, further comprising electrical circuitry configuredto drive the one or more LED dies with a maximum input power that isless than about 50% of a rated maximum power of the one or more LED dieswhile achieving a luminescence of at least about 800 mW/cm².
 8. A dentalcuring light device as in claim 1, further comprising electricalcircuitry configured to drive the one or more LED dies with a maximuminput power that is less than about 40% of a rated maximum power of theone or more LED dies while achieving a luminescence of at least about2000 mW/cm².
 9. A dental curing light device as recited in claim 1,wherein the thermally conductive layer comprises a piece separate fromthe device body and has a thickness in a range from about 500 microns toabout 900 microns.
 10. A dental curing light device as recited in claim1, wherein the thermally conductive layer has a thermal conductivity ofat least about 170 W/m-K.
 11. A dental curing light device as recited inclaim 1, wherein the thermally conductive layer has a higher thermalconductivity than the body material of the device body.
 12. A dentalcuring light device as recited in claim 1, wherein the thermallyconductive layer is selected from the group consisting of aluminumnitride, beryllium oxide, diamond, silicon carbide, boron nitride, andcombinations thereof.
 13. A dental curing light device as recited inclaim 1, wherein the thermally conductive layer is thermally coupled tothe substrate by a thermally conductive adhesive.
 14. A dental curinglight device as recited in claim 1, wherein the thermally conductivebody material of the device body includes a metal selected from thegroup consisting of aluminum, copper, magnesium, and alloys thereof. 15.A dental curing light device as recited in claim 1, wherein the devicebody includes a neck portion and a handle portion, the neck portion andthe head portion having a thickness between about 1 mm and about 10 mmso as to be sized and configured for insertion into an oral cavity of apatient, the handle portion having a thickness between about 15 mm andabout 30 mm so as to be sized and configured for gripping by a dentalpractitioner.
 16. A dental curing light device as in claim 1, whereinthe one or more LED dies includes a first LED die that emits in the blueregion of the light spectrum and a second LED die that emits in theultraviolet (UV) region of the light spectrum.
 17. A dental curing lightdevice as in claim 1, further comprising a lens or a photonic crystal onthe head portion of the device body, the lens or photonic crystal beingconfigured to focus light emitted from the LED die.
 18. A dental curinglight device as in claim 17, further comprising an anti-reflectivecoating on at least a portion of the lens.
 19. A dental curing lightdevice as in claim 17 further comprising a reflective collar having areflective coating on an interior surface thereof, the collar beingpositioned between the LED die and the lens or photonic crystal, thereflective collar defining an opening configured to reflect and channellight from the LED die into the lens or photonic crystal.
 20. A dentalcuring light as in claim 19, wherein the reflective coating comprises anoble metal.
 21. A dental curing light device as in claim 1, wherein thehead portion of the device body includes a receptacle and a thermallyconductive removable member, the removable member being configured to beremovably attached within the receptacle, wherein the LED assembly andthe thermally conductive layer comprise portions of the removablemember.
 22. A dental curing light device as in claim 1, wherein thethermally conductive layer includes traces in electrical contact withthe contacts of the LED assembly.
 23. A dental curing light device as inclaim 1, wherein the thermally conductive layer comprises a printedcircuit board.
 24. A dental curing light device as in claim 23, whereinthe thermally conductive layer comprises at least one of a ceramicprinted circuit board or a metalized printed circuit board.
 25. A dentalcuring light device as in claim 1, wherein the thermally conductivelayer includes a thermally conductive grease or gel having one or morethermally conductive filler materials.
 26. A dental curing light deviceas in claim 1, wherein the thermally conductive layer includes athermally conductive grease selected from the group consisting ofsilicon grease, polymer grease, metalized grease, nano-particle grease,and combinations thereof.
 27. A dental curing light device as in claim1, wherein the thermally conductive layer includes a deformable pad. 28.A dental curing light device as in claim 27, wherein the deformable padis a thermally conductive grease or gel.
 29. A dental curing lightdevice having a thermally conductive layer for dissipating heat from anLED, comprising: a device body having a proximal end and a distal end,the device body being formed of a thermally conductive body material,the device body including a handle portion, a neck portion, and a distalhead portion, the head portion being configured to support or contain anLED assembly, the handle portion having a cavity for receiving anelectronics assembly; an LED assembly thermally coupled to the headportion of the device body, the LED assembly including one or more LEDdies and a thermally conductive LED assembly substrate, the one or moreLED dies being electrically coupled to one or more contacts on the LEDassembly, the one or more LED dies being configured to emit a spectrumof light capable of curing a light curable composition; and a thermallyconductive layer that thermally couples the LED assembly with the devicebody, wherein a surface area coupling the thermally conductive layerwith the device body is sufficient to conduct away a majority of wasteheat generated by the one or more LED dies with the light curing deviceset to a highest power setting; and an electronics assembly positionedwithin the cavity of the handle portion, the electronics assemblyincluding a user selectable switch and circuitry configured to drive theone or more LED dies to emit light at an intensity of at least about2000 mW/cm².
 30. A dental curing light device as recited in claim 29,further comprising a protective coating covering at least a portion ofthe device body between the head portion and the handle portion.
 31. Adental curing light device as recited in claim 30, wherein theprotective coating includes at least one of a fluoropolymer or parylene.32. A dental curing light device as recited in claim 29, wherein theelectronics assembly is configured to ramp the light intensity over aperiod of time and wherein the electronics assembly provides forselection of longer and shorter periods of time for the ramp period. 33.A dental curing light device as in claim 32, wherein a first ramp timeis in a range from about 3 to about 7 seconds, and a second ramp time isin a range from about 8 to about 12 seconds.
 34. A method for using adental curing light, comprising: providing a dental curing light asrecited in claim 1; depositing a light curable composition within anoral cavity of a patient, and operating the dental curing light todirect a light beam of at least 800 mW/cm² toward the curablecomposition for a sufficient amount of time to cure the curablecomposition.
 35. A method as in claim 34, wherein the light beamdirected toward the curable composition has a total light output of atleast about 2000 mW/cm².
 36. A method as in claim 34, wherein the one ormore LED dies are driven at less than about 70% of a rated maximum powerof the LED assembly.
 37. A method as in claim 34, wherein the one ormore LED dies are driven at less than about 50% of a maximum rated powerof the LED assembly.
 38. A dental curing light device having a thermallyconductive layer for dissipating heat from an LED die, comprising: adevice body having a proximal end and a distal end, the device bodybeing formed of a thermally conductive material, the device bodyincluding a head portion, the head portion being configured to supportone or more LED dies; one or more LED dies thermally coupled to the headportion of the device body, the one or more LED dies being configured toemit a spectrum of light capable of curing a light curable composition;a thermally conductive layer on the head portion of the device body, thethermally conductive layer thermally coupling the LED dies with thedevice body; and electrical circuitry configured to drive the one ormore LED dies with a maximum input power that is less than about 70% ofa rated maximum power of the one or more LED dies while achieving aluminescence of at least about 500 mW/cm².
 39. A dental curing lightdevice as in claim 38, wherein the electrical circuitry is configured todrive the one or more LED dies with a maximum input power that is lessthan about 50% of a rated maximum power of the one or more LED dieswhile achieving a luminescence of at least about 800 mW/cm².
 40. Adental curing light device as in claim 38, wherein the electricalcircuitry is configured to drive the one or more LED dies with a maximuminput power that is less than about 40% of a rated maximum power of theone or more LED dies while achieving a luminescence of at least about800 mW/cm².
 41. A dental curing light device as in claim 38, wherein theelectrical circuitry is configured to drive the one or more LED dieswith a maximum input power that is less than about 50% of a ratedmaximum power of the one or more LED dies while achieving a luminescenceof at least about 2000 mW/cm².
 42. A dental curing light device as inclaim 38, wherein the electrical circuitry is configured to drive theone or more LED dies with a maximum input power that is less than about50% of a rated maximum power of the one or more LED dies while achievinga luminescence of at least about 3000 mW/cm².
 43. A dental curing lightdevice comprising: a single piece body extending from a proximal end toa distal head end, the body including a handle portion disposed adjacentthe proximal end and extending towards the distal end, the entirety ofthe body comprising a single piece of thermally conductive material soas to eliminate seams within the body, the single piece body having acontrol assembly hole at the handle portion for receiving a controlassembly; a control assembly comprising a control panel and a controlcircuit board, the control assembly being received within the controlassembly hole at the handle portion of the body; and one or more LEDdies disposed at a distal end of the dental curing light device suchthat heat generated during use of the LED dies is dissipated into thesingle piece metal body, which acts as a heat sink for the one or moreLED dies.
 44. A dental curing light device as recited in claim 43,wherein the entirety of the single piece body comprises a metal selectedfrom the group consisting of aluminum, copper, magnesium, and alloysthereof.
 45. A dental curing light device as recited in claim 43,wherein the entirety of the single piece body comprises an aluminumalloy.
 46. A dental curing light device as recited in claim 43, whereinthe entirety of the single piece body comprises a thermally conductiveceramic fiber selected from the group consisting of carbon fiber, boronfiber, boron nitride fiber, and combinations thereof.
 47. A dentalcuring light device as recited in claim 43, wherein the entirety of thesingle piece body comprises graphene.
 48. A dental curing light deviceas recited in claim 43, wherein the entirety of the single piece body isformed by machining a single piece of material.
 49. A dental curinglight device as recited in claim 43, wherein the single piece bodyfurther comprises an LED head assembly hole at the distal head end ofthe body, and the one or more LED dies are disposed on an LED headassembly that is separate from the single piece body, the LED headassembly being received within the LED head assembly hole of the singlepiece body such that heat generated during use of the LED dies isdissipated into the single piece metal body, which acts as a heat sinkfor the LED dies.
 50. A dental curing light device as recited in claim49, wherein the LED head assembly has a mass no more than about 10% ofthe mass of the single piece body.
 51. A dental curing light device asrecited in claim 49, wherein the LED head assembly has a mass no morethan about 5% of the mass of the single piece body.
 52. A dental curinglight device as recited in claim 43, the single piece body furthercomprising a power cord hole at the proximal end of the body throughwhich a power cord may be coupled to the control assembly.
 53. A dentalcuring light device comprising: a single piece body extending from aproximal end to a distal head end, the body including a handle portiondisposed adjacent the proximal end and extending towards the distal end,the entirety of the body comprising a single piece of thermallyconductive material so as to eliminate seams within the body, the singlepiece body having an LED head assembly hole at the distal head end forreceiving an LED head assembly, and a control assembly hole at thehandle portion for receiving a control assembly; an LED head assemblycomprising an LED, the LED head assembly being received into the LEDhead assembly hole at the distal head end of the body such that heatgenerated during use of the LED head assembly is dissipated into thesingle piece metal body, which acts as a heat sink for the LED; and acontrol assembly comprising a control panel and a control circuit board,the control assembly being received within the control assembly hole atthe handle portion of the body.
 54. A dental curing light devicecomprising: a single piece body extending from a proximal end to adistal head end, the body including a handle portion disposed adjacentthe proximal end and extending towards the distal end, the entirety ofthe body comprising a single piece of thermally conductive material soas to eliminate seams within the body, the single piece body having acontrol assembly hole at the handle portion for receiving a controlassembly; a control assembly comprising a control panel and a controlcircuit board, the control assembly being received within the controlassembly hole at the handle portion of the body; a thin electricallyinsulative and thermally conductive layer formed over at least thedistal head end of the single piece body, the thin electricallyinsulative and thermally conductive layer having a thickness betweenabout 0.05 micron and about 50 microns; and one or more LEDsemiconductor dies directly mounted on the thin electrically insulativeand thermally conductive layer formed over the distal head end of thebody, wherein the electrically insulative and thermally conductive layerelectrically insulates the one or more LED dies from the underlyingsingle piece body, which acts as a heat sink for the one or more LEDdies.
 55. A dental curing light device as recited in claim 54, whereinthe entirety of the single piece body comprises a metal selected fromthe group consisting of aluminum, copper, magnesium, and alloys thereof.56. A dental curing light comprising: an elongate body having a proximalend and a distal head end, the body being formed of a thermallyconductive material; a thin electrically insulative and thermallyconductive layer formed over at least a portion of an exterior surfaceof the thermally conductive material at the distal head end of theelongate body, the electrically insulative and thermally conductivelayer having a thickness between about 0.05 micron and about 50 microns;and one or more LED dies configured to emit a spectrum of light capableof curing a light curable composition, the one or more LED dies beingmounted on the distal head end of the elongate body, wherein theelectrically insulative and thermally conductive layer electricallyinsulates the one or more LED dies from the thermally conductivematerial of the elongate body.
 57. A dental curing light device asrecited in claim 56, wherein the elongate body comprises a metalselected from the group consisting of aluminum, copper, magnesium, andalloys thereof.
 58. A dental curing light as recited in claim 56,further comprising a photonic crystal disposed so as to receive andcollimate light emitted by the one or more LED dies.
 59. A dental curinglight as recited in claim 56, wherein the thin electrically insulativeand thermally conductive layer has a thickness between about 0.1 micronand about 10 microns.
 60. A dental curing light as recited in claim 56,wherein the thin electrically insulative and thermally conductive layerhas a thickness between about 0.2 micron and about 1 micron.
 61. Adental curing light device comprising: a device body having a handleportion, a neck portion, and a head portion, the head portion configuredto support or contain one or more LED dies, the handle portion having acavity for housing an electronics assembly, wherein at least a portionof each of the handle portion, the neck portion, and the head portionform a single piece of a thermally conductive material; one or more LEDdies positioned on or within the head portion, the one or more LED diesbeing configured to emit a spectrum of light capable of curing a lightcurable composition; a fluoropolymer or parylene coating covering atleast a portion of the neck portion and the head portion of the devicebody.
 62. A dental curing light device as recited in claim 61, whereinthe fluoropolymer or parylene coating covers substantially all of anexterior surface of the head and neck portions of the device body.
 63. Adental curing light device as recited in claim 61, wherein thefluoropolymer or parylene coating covers substantially all of anexterior surface of the handle portion, neck portion, and head portionof the device body.
 64. A dental curing light device as recited in claim63, wherein, the fluoropolymer or parylene coating comprisespolytetrafluoroethylene.
 65. A dental curing light device, comprising:device body having a handle portion, a neck portion and a head portion,the head portion configured to support one or more LED dies, the handleportion having a cavity for housing an electrical switch, the devicebody comprising a thermally conductive material; and one or more LEDdies disposed on the head portion, the LED dies being configured to emita spectrum of light capable of curing a light curable composition; ascratch resistant coating covering at least a portion of the neckportion and the head portion of the device body; and a fluoropolymer orparylene coating covering at least a portion of the neck portion and thehead portion of the device body.
 66. A dental curing light device asrecited in claim 65, wherein the scratch resistant coating comprises atleast one of Al₂O₃ or AlN.
 67. A dental curing light device as recitedin claim 65, wherein the fluoropolymer or parylene coating coverssubstantially all of an exterior surface of the head and neck portionsof the device body.
 68. A dental curing light device as recited in claim65, wherein the fluoropolymer or parylene coating covers substantiallyall of an exterior surface of the handle portion, neck portion, and headportion of the device body.
 69. A dental curing device as recited inclaim 65, wherein, the fluoropolymer or parylene coating comprisespolytetrafluoroethylene.
 70. A method of manufacturing a dental curinglight, comprising: providing a device body comprising a thermallyconductive material, the device body comprising a single piece ofmaterial that includes a handle portion, a neck portion and a headportion, the handle portion having a cavity configured to receive anelectronics assembly, the head portion including at least one LED die;applying a scratch resistant coating to an exterior surface of at leasta portion of the device body; and depositing a fluoropolymer or parylenecoating over at least portion of the scratch resistant coating.
 71. Amethod as recited in claim 70, wherein the scratch resistant coatingcomprises at least one of Al₂O₃ or AlN.
 72. A method as recited in claim70, wherein the fluoropolymer or parylene coating covers substantiallyall of an exterior surface of the head and neck portions of the devicebody.
 73. A method as recited in claim 70, wherein the fluoropolymer orparylene coating covers substantially all of an exterior surface of thehandle portion, neck portion, and head portion of the device body.
 74. Amethod as recited in claim 70, wherein the fluoropolymer or parylenecoating comprises polytetrafluoroethylene.